Inertial sensors are a vital navigation tool in modern transportation and military applications. In addition, inertial sensors are finding increased use in a wider range of applications, including automotive safety and control systems, video game controllers, and automobile navigation systems. Inertial devices are used to detect acceleration in one or more directions. They generally comprise an element that moves relative to another body, wherein the moving element moves in response to an acceleration. The movement of the moving element induces a variation of an electrical signal, which is provided a control circuit.
Recently, the use of MEMS technology has been proposed for inertial movement-detection sensors. MEMS inertial sensors comprise a mobile part and a fixed part, typically both of a conductive material (e.g., silicon and/or metal). In many cases, the mobile part comprises a suspended element that moves substantially linearly with respect to the fixed part in response to an acceleration. Often these parts are capacitively coupled so that a movement of the mobile part with respect to the fixed part brings about a capacitance variation that is detectable by an associated sense circuit.
Development of these devices, however, has primarily been focused on single-axis micro-gyroscopes and multi-axis accelerometers. Such prior-art sensors typically perform detection of the movement in one, or at the most two, preferential directions of detection. In order to detect movement in additional directions, it is necessary to replicate the sensor an appropriate number of times. This can lead to an increase in overall device size, higher cost, and increased sense circuit complexity. Such drawbacks have provided a barrier to the development and adoption of single-chip multi-axis inertial sensors.
A cost-effective, single-chip, multi-axis inertial sensor, therefore, would represent a significant advance in the state of the art.